High throughput features in 11s mesh networks

ABSTRACT

The addition of high throughput capability elements to beacon frames and peer link action frames in wireless mesh networks enable the utilization of desirable features without further modifications to the network. Rules can be established for high throughput mesh point protection in a mesh network, Space-time Block Code (STBC) operations and 20/40 MHz operation selections. However, features such as PSMP (power save multi-poll) and PCO (phased coexistence operations) are barred from implementation to prevent collisions.

RELATED APPLICATION

The present invention is a divisional of U.S. patent application Ser.No. 12/687,695 filed Jan. 14, 2010, which claims the benefit of priorityto United States Provisional Patent Application no. 61/144,678 filedJan. 14, 2009, both of which are incorporated herein by reference intheir entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate, in general, to highthroughput channel operation in a mesh wireless local area network.

2. Relevant Background

The Institute of Electrical and Electronics Engineers (IEEE) 802.11s isa draft IEEE 802.11 amendment for mesh networking, defining how wirelessdevices can interconnect to create a WLAN mesh network, which may beused for static topologies and ad-hoc network. 802.11 is generally a setof IEEE standards that govern wireless networking transmission methods.A wireless mesh network is a communications network made up of radionodes organized in a mesh topology. Wireless mesh networks often consistof mesh clients, mesh routers and gateways. The mesh clients are oftenlaptops, cell phones and other wireless devices while the mesh routersforward traffic to and from the gateways which may, but need not,connect to the Internet. The coverage area of the radio nodes working asa single network is sometimes called a mesh cloud. Access to this meshcloud is dependent on the radio nodes working in harmony with each otherto create a radio network. A mesh network is reliable and offersredundancy. When one node can no longer operate, the rest of the nodescan still communicate with each other, directly or through one or moreintermediate nodes.

In the initial Wireless Local Area Network (WLAN) technology, a datarate of 1 to 2 Mbps was supported by the use of frequency hopping,spread spectrum, and infrared communication using a frequency of 2.4 GHzin accordance with the IEEE 802.11 standard. Today IEEE 802.11n providesup to 600 Mbps. The IEEE 802.11 standard has developed or is developinga variety of technical standards for improvement in quality of service(QoS), compatibility of an access point (AP) protocol, securityenhancement, wireless resource measurement, wireless access in vehicularenvironment, fast roaming, wireless mesh network, inter-working withexternal networks, wireless network management, and the like.

FIG. 1 is a diagram of a mesh network 100 in accordance with the presentinvention and as known to one skilled in the relevant art. The meshnetwork 100 comprises a plurality of interconnected mesh points 130,135. The mesh network 100 may also include a mesh portal 120. The meshportal 120 is a mesh point that has a connection with an externalnetwork 110, (e.g., a wired network). Some of the mesh points may bemesh APs 135. Each of the mesh APs 135 is a mesh point that also worksas an AP in its own basic service set 160, 170. A mesh AP 135 can act,in one instance, as a non-mesh AP to serve local stations 150 in its BSS160, 170, and in another instance, act as a wireless bridge to receive,forward and route packets through the mesh network 100.

Recall that a “wireless mesh network” can support direct communicationbetween plural wireless stations having a relay function. In view offunctionality, a distribution system (DS) for plural APs can be replacedwith an inter-operable wireless link or a multi-hop path between theplural wireless stations. In the mesh network, one wireless station canset up a peer-to-peer wireless link (peer link) with one or moreneighboring wireless stations, thereby constructing a more flexiblenetwork. Thus, plural communication paths can exist between two wirelessstations. Among them, the direct communication paths between twowireless stations are called a wireless mesh link or a mesh peer link ora peer link. In a mesh network, wireless stations are called mesh points(MP). A wireless station performing the function of an AP is called amesh access point (MAP).

Such a wireless mesh network has advantages, such as flexibility inconstructing a network, reliability due to bypass paths, reduction inpower consumption due to a decrease in communication distance. Morespecifically, it is possible to construct a flexible network by usingthe mesh network even in places not including any wired communicationnetwork. In the mesh network, the plural MPs can be connected to eachother to guarantee plural bypass paths. Accordingly, even when one MP isout of order, data can be transmitted through another path. In the meshnetwork, since the communication can be made through a neighboring MP,it is possible for terminals to communicate with lower power.

IEEE 802.11s provides a means to form a mesh wireless backhaul with IEEE802.11 WLAN technology. Mesh networks, also known as multi-hop networks,enable data packets to be relayed more than once in order to reach theirdestination. This presents a different paradigm as compared to theoriginal WLAN standard, which addresses only star topologies forstations (STAs) to be connected to an access point, effectively usingsingle hop communications through a basic service set (BSS).

IEEE 802.11s addresses network nodes that form a mesh network and theWLAN mesh operation in the backhaul that is transparent to all STAs.This means that, similar to legacy IEEE 802.11 WLAN, STAs still connectto an AP, (i.e., mesh AP having a mesh capability), through a BSS. Themesh AP interfaces to other mesh points, which forward and route trafficthrough the mesh network to a destination. The destination may be a meshportal, which routes the traffic to the external network, or may beanother mesh AP attached to the mesh network. By choosing this approach,even legacy STAs may still operate in a mesh-enabled WLAN. Thecommunication between STAs and a mesh AP in a BSS is completelyindependent from the mesh network.

The IEEE 802.11n is another specification for providing a highthroughput (HT) WLAN. Some of the IEEE 802.11n throughput-enhancingfeatures are aggregation, enhanced block acknowledgement (BA), reversedirection grant, power save multiple poll (PSMP), and operationalbandwidth. In IEEE 802.11n, a data rate is increased by annexing orbonding two adjacent channels. The data rate increase is also achievedby using several more data tones, with 802.11 40 MHz operation relativeto 2.times.20 MHz channel occupancy with 802.11a/g. However, not allIEEE 802.11n devices may support 40 MHz operation and, therefore, thetransition of operation from 20 MHz to 40 MHz must be managedefficiently. In order to achieve this, the IEEE 802.11n standardprovides some channel management mechanisms.

In IEEE 802.11n, three operating modes are allowed according tobandwidth and BSS capability: 20 MHz operation, 20/40 MHz operation andPhased Coexistence Operation (PCO). Each of these modes has associatedrules of operation. In a 20 MHz operation, all STAs will operate only ina 20 MHz mode whether or not the STAs are 20 MHz or 20/40 MHz capable.In a 20/40 MHz operation, STAs choose the bandwidth by using atransmission channel width action message. In addition, a 40 MHz devicewill protect its transmission with legacy control frames, such asrequest-to-send (RTS) or clear-to-send (CTS) frames, if the AP of itsBSS indicates that there are 20 MHz and/or legacy STAs in the BSS. Inthe PCO mode, which is an optional mechanism, the BSS alternates between20 MHz and 40 MHz modes.

There are three operation modes in the current 802.11 standard:infrastructure BSS, independent BSS and mesh network. In infrastructureBSS, an AP is the controller of the BSS. In independent BSS, there is nocentral controller and no association between STAs. In mesh network,there is no central controller but neighbor MPs associated with eachother. 802.11n has features that does not require central controller orpeer coordination, and features that require central controller or peercoordination.

The features that do not require central controller or peer coordinationcan be used in a mesh network without any change after the addition ofHT capability to beacon and peer link frames. These capabilities includeAggregated-MAC Service Data Unit (A-MSDU), Aggregated-MAC Protocol DataUnit (A-MPDU), enhanced block acknowledgement, reverse direction grant,beam forming and antenna selection (ASEL).

In IEEE 802.11s, HT information elements control the operation of HTSTAB in the mesh network. To effect such control, an infrastructure BSSuses all fields in the HT information element to define the operation ofthe HT STAB independent BSS use fields that are not reserved to definethe operation of HT STAB. Unfortunately, it is unclear what fields willbe used or reserved in a mesh network, and it is not clear how featuressuch as power save multi-poll, HT protection, Space Time Block Coding(STBC) operation, 20/40 MHz operation, and phased coexistence operationswill be used, or whether features such as PSMP or PCO operations shouldbe allowed at all.

A need therefore exists to identify HT features in a IEEE 802.11s meshnetwork. These and other deficiencies of the prior art are addressed byone or more embodiments of the present invention.

SUMMARY OF THE INVENTION

The addition of HT capability elements to beacon frames and peer linkaction frames in wireless mesh networks enable features such as A-MSDU,A-MPDU, Enhanced BlockAck, reverse direction, beam forming and antennaselection to be used without further modifications. Rules can beestablished for HT mesh point protection in a mesh network, Space-timeBlock Code (STBC) operations, and 20/40 MHz operation selections.However, HT features such as PSMP and PCO operations should bedisallowed in wireless mesh networks.

The features and advantages described in this disclosure and in thefollowing detailed description are not all-inclusive. Many additionalfeatures and advantages will be apparent to one of ordinary skill in therelevant art in view of the drawings, specification, and claims hereof.Moreover, it should be noted that the language used in the specificationhas been principally selected for readability and instructional purposesand may not have been selected to delineate or circumscribe theinventive subject matter; reference to the claims is necessary todetermine such inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned and other features and objects of the presentinvention and the manner of attaining them will become more apparent,and the invention itself will be best understood, by reference to thefollowing description of one or more embodiments taken in conjunctionwith the accompanying drawings, wherein:

FIG. 1 shows a wireless mesh network as applicable to the presentinvention and as known in the prior art;

FIG. 2 is a flowchart of one embodiment of the present invention forestablishing mutual high throughput protection in a wireless meshnetwork

FIGS. 3A and 3B taken together is a flowchart of a method embodiment ofthe present invention for establishing high throughput protection in awireless mesh network; and

FIG. 4 is a flow chart of a method embodiment of the present inventionfor establishing high throughput communications between STBC mesh pointsin a wireless mesh network.

The Figures depict embodiments of the present invention for purposes ofillustration only. One skilled in the art will readily recognize fromthe following discussion that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles of the invention described herein.

DESCRIPTION OF THE INVENTION

Embodiments of the present invention are hereafter described in detailwith reference to the accompanying Figures. Although the invention hasbeen described and illustrated with a certain degree of particularity,it is understood that the present disclosure has been made only by wayof example and that numerous changes in the combination and arrangementof parts can be resorted to by those skilled in the art withoutdeparting from the spirit and scope of the invention.

As previously described, a wireless mesh network can support directcommunication between a plurality of mesh points. The distributed APsare coupled with an inter-operable wireless link, or multi-hop path,between the wireless stations. In such a wireless mesh network, onewireless station can set up a peer-to-peer wireless link with one ormore neighboring stations, thus forming a network. This forms multiplecommunication paths between two wireless stations. When two stationsform a direct communication path, such a path is called a mesh peer linkor simply a peer link.

In such a wireless mesh network, a beacon frame is a frame comprisingmanagement information about the wireless network. Beacon frames aretransmitted by mesh points periodically to announce the presence andconfiguration of a wireless mesh network. Typically in BSS networkbeacon frames are transmitted from an AP within a BSS so that other STAswithin the BSS will be aware of the BSS structure. In an independent BSSnetwork, beacon generation is distributed among the stations within thenetwork.

Aspects of the present invention relate to HT capability in a meshnetwork. Specifically, the addition of HT capability in beacon framesand peer link action frames are addressed.

According to one embodiment of the present invention, two HT featuresare barred from implementation in a mesh network. These HT featuresinclude PSMP (power save multi-poll) and PCO (phased coexistenceoperations). In frame transmissions between devices in a wirelesscommunication system that implements power saving multi-poll, a powersaving sequence begins with the transmission of an un-aggregated powersave multi-poll frame, and terminates when the last scheduled uplinktransmission ends.

IEEE 802.11n provides a high data rate WLAN standard which allows amaximum throughput of at least 130 Mbps. The amended n specificationprovides a power management scheme termed PSMP. Frame transmissionsbetween an AP and a STA implements PSMP.

The PSMP frame is a broadcast/multicast packet. As a result, it ishighly likely that such a packet can collide with other simultaneoustransmissions. Conventional approaches suitable for protecting unicastpackets are also not effective in protecting the PSMP frame againstcollisions. For example, an RTS/CTS exchange has conventionally beenused to protect unicast packet delivery. However, this is not suitablefor broadcast/multicast packets such as the PSMP frame.

Another conventional approach is to transmit the PSMP MPDU at a baserate or to precede the transmission of the PSMP MPDU by a CTS (i.e.,CTS-to-self) frame with the receiver address (RA) field set to theinitiator's (e.g., the AP's) own media access control (MAC) address.However, neither approach can fully protect the PSMP frame sequence ifoverlap BSS cannot be reached by AP's transmission. Therefore, it isquite possible that the PSMP frame is not correctly received by one ormore PSMP-enabled STAs in a PSMP sequence.

Nonetheless, a PSMP sequence allows the AP to create effective serviceperiods for Automatic Power Save Delivery (APSD). Multiple-TrafficIdentifiers (TID) BlockAck can allow for single frames to respond toimplicit BAR over multiple-TID; but, as previously stated, a 2-hop MPmay create more collisions when a distributed channel access (EDCA) isused for PSMP, as no RTS/CTS protection for the downlink burst can beused.

One alternative is to combine mesh coordinated channel access (MCCA) andPSMP. Such a combination is likely to increase link efficiency, however,the merger of PSMP and MCCA alters the original mechanism of MCCA sinceEDCA or PIFS of the highest access category will be used by the MP. Theresult will be multiple access category frames being transmitted in aMCCA transmitting operation, and the mesh point will send unicast framesto more than one destination MP. For at least these reasons, PSMP is notsuited for HT wireless mesh network communications under 802.11s.

Another mode of operation which is not suited for operation in awireless mesh network is phased co-existence operations (PCO). In IEEE802.11n, three operating modes are allowed according to bandwidth andBSS capability: 20 MHz operation, 20/40 MHz operation and PhasedCoexistence Operation (PCO). In the PCO mode, the BSS alternates between20 MHz and 40 MHz modes. In the 20 MHz phase, independent BSS activityis allowed on the control channel and on the extension channel. In a 40MHz phase, 40 MHz transmissions occur across the 40 MHz channel.However, the 40 MHz HT frames in the 40 MHz phase are not protected witha hidden 20 MHz MP. If two 40 MHz MPs have overlapped phases, when afirst MP ends its 40 MHz phase using CF-end, the second MP's 40 MHzphase may also, inadvertently, be ended. As a result, data may be lost.Thus, as with PSMP, PCO HT operations should not be allowed in 802.11smesh network operations.

While according to one embodiment of the present invention, PSMP and PCOHT features are prevented from implementation in a mesh network under802.11s, other features can be effectively used. Under the correctmethodology HT protection, STBC operations and 20/40 MHz operationsections can be effectively implemented.

In order to allow two or more MPs to set up peer links with each otherto form a mesh network or to allow a different MP to participate in anexisting mesh network, the mesh profiles of the MPs to set up the peerlinks should be necessarily equal to each other. The MPs support atleast one mesh profiles. The mesh profile includes a mesh ID, a pathselection protocol ID, and a path selection metric ID. The mesh profilemay further include a congestion control mode ID.

A MP also having the function of an AP is particularly called a MAP.Accordingly, the MAPs in a mesh network also perform the function of anAP for wireless stations associated therewith. The AP may be calledconvergence controller, BS, node-B, or site controller, in addition tothe title of access point.

Since the mesh profiles of the MPs should be necessarily equal to eachother to participate in a mesh network for communication, the MPs shouldhave sufficient information element on themselves and the neighboringMPs. Procedures of allowing an MP to participate in a mesh network, todetect the change in connectivity in the mesh network, and to react withthe change include a mesh discovery procedure and a mesh peer linkmanagement procedure in the mesh network. The mesh discovery procedureis to allow an MP to discover latent neighboring MPs, by passivescanning using beacon frames transmitted from the neighboring MPs oractive scanning using the exchange of probe request frames and proberesponse frames between two MPs, and to discover neighboring MPs havingthe same mesh profile among the latent neighboring MPs (peer link). Themesh peer link management procedure is used to set up the peer linksbetween the MPs, to manage the peer links, and to tear down the peerlinks.

As described above, the mesh discovery procedure is designed to detectcandidate peer MPs and characteristics thereof, and includes proceduresbefore and after the MPs participate in the mesh network. The configuredMP has at least one mesh profile. When the MP is a member of a specificmesh network, one mesh profile is accurately activated.

The mesh discovery procedure for discovering the neighboring MPsincludes allowing the MP to perform passive or active scanning. In thecase of the active scanning, a first MP transmits a probe request frameincluding the mesh ID information. Only second MPs having the same meshID information among the MPs having received the probe request frametransmits a probe response frame in response thereto. The probe responseframe includes a mesh configuration element. The first MP can knowprofile information of the second MPs, having transmitted the proberesponse frame on the basis of the information included in the meshconfiguration element. Thus a peer link is established.

Another mesh discovery procedure for discovering the neighboring MPsuses beacon frames periodically transmitted from the neighboring MPs.Since beacon frames transmitted from the MPs in the mesh network includethe mesh ID information and the mesh configuration information, the MPreceiving the beacon frames can know the mesh profile of thetransmitting MP. The mesh configuration information included in thebeacon frame is substantially the same as the information included inthe probe request frame or the probe response frame, and thus, detaileddescription thereof is omitted.

When an MP discovers the neighboring MPs using one of theabove-mentioned mesh discovery procedures, the MP tries to perform themesh link setup procedure with the discovered neighboring MPs. The meshlink setup procedure is to set up logical links between the MPs and is aprocedure for setting up peer links between the MPs, which is alsocalled a peering procedure. In the mesh network, the MPs can transmitand receive data frames or management frames (except for managementframes for the mesh discovery procedure or the peer link managementprocedure) after the mesh peer links are set up by the peeringprocedure. The MPs transmit and receive a peer link open frame and apeer link confirmation frame to set up the mesh peer links between theMPs.

When the MP transmitting the beacon frame, association frame, peer linkopen frame is an MP supporting HT, that is, an HT MP, the body portionof the beacon frame, association frame, open frame includes an HTinformation element or an HT operation information element. The HTinformation element or the HT operation information element includesinformation for controlling the operation of the HT MP in the meshnetwork. The HT capability information element is used to notify to theopposite MP that the HT MP supports HT. The HT capability informationelement should necessarily be included in the peer link to use the HTservice in the mesh network. Accordingly, the HT MP transmits to theopposite MP the HT feature indicating that it supports HT functions.

According to one embodiment of the present invention, one of thesupported HT features is HT protection. HT transmissions are protectedbased on HT protection, non-green HT STAs present in the mesh network,OBSS non-HT STAs present in the mesh network, and L-SIG transmitoperations having full protection support. In a mesh network having a HTBSS, HT protection can be set to one of several modes. These modesinclude: 1) HT no protection mode; 2) HT non-member protection mode; 3)HT 20 MHz protection mode; and 4) HT non-HT mixed mode. The selection ofone of these modes is dependent on the mesh network environment.

In an independent BSS, the HT protection field is reserved. However, anHT STA can protect transmissions just as if fields are set to aprotective mode. For example, if the HT STA fields are set so as to haveHT protection set to non-HT mixed, RIFS of HT information element set to1, non-green field HT STA present field set to 1, L-SIG transmitoperation full support field set to 0, OBSS non-HT STA set to 1 and PCOactive field set to 0, the STA will protect the HT transmission.

In a non-HT BSS, an HT STA operating a direct link (peer) with anotherHT STA can also operate to protect HT transmissions. Again, the STA willprotect the HT transmission when the HT STA fields are set so as to haveHT protection set to non-HT mixed, RIFS of HT information element set to1, non-green field HT STA present field set to 1, L-SIG transmitoperation full support field set to 0, OBSS non-HT STA set to 1, PCOactive field set to 0 and basic MCS field set to 0.

One embodiment of the present invention identifies that HT transmissionsfrom a STA in a mesh network can be protected based on the capabilitiesof its neighboring STAs. FIG. 2 shows a flowchart of a method forestablishing a mutual high throughput protection mode between a pair ofmesh points so that the two mesh points can communicate. At a basiclevel, the high throughput communication begins 205 with theidentification 210 of the protection mode of a mesh point and itsneighbors. Thereafter, a mutual high throughput protection mode can beestablished 260 such that communications can exist 295 between a meshpoint and each of its neighbors. Note that a mesh point may interactwith several neighboring mesh points, each with differing highthroughput protection modes. The present invention enables highthroughput protection communications to occur in a wireless mesh networkcharacterized by multiple high throughput protection modes.

Included in the following description are flowcharts depicting examplesof the methodology which may be used to facilitate high throughputcommunications between mesh points in a wireless mesh network. In thedescription, it will be understood that each block of the flowchartillustrations, and combinations of blocks in the flowchartillustrations, can be implemented by computer program instructions.These computer program instructions may be loaded onto a computer orother programmable apparatus to produce a machine such that theinstructions that execute on the computer or other programmableapparatus create means for implementing the functions specified in theflowchart block or blocks. These computer program instructions may alsobe stored in a computer-readable memory that can direct a computer orother programmable apparatus to function in a particular manner suchthat the instructions stored in the computer-readable memory produce anarticle of manufacture including instruction means that implement thefunction specified in the flowchart block or blocks. The computerprogram instructions may also be loaded onto a computer or otherprogrammable apparatus to cause a series of operational steps to beperformed in the computer or on the other programmable apparatus toproduce a computer implemented process such that the instructions thatexecute on the computer or other programmable apparatus provide stepsfor implementing the functions specified in the flowchart block orblocks.

Accordingly, blocks of the flowchart illustrations support combinationsof means for performing the specified functions and combinations ofsteps for performing the specified functions. It will also be understoodthat each block of the flowchart illustrations, and combinations ofblocks in the flowchart illustrations, can be implemented by specialpurpose hardware-based computer systems that perform the specifiedfunctions or steps, or combinations of special purpose hardware andcomputer instructions.

FIGS. 3A and 3B taken together is a detailed flowchart of a method forestablishing high throughput protection modes fostering high throughputcommunications between mesh points. According to one embodiment of thepresent invention, a HT MP can set its protection mode according to thecapabilities of its neighboring MPs and STAs in the primary channel orin the secondary channel in a 20/40 MHz mesh network.

When two peer MPs report the same HT protection mode in the HTprotection field, protection methods related to that mode will be usedin the BSS. When two peer MPs report differing protection modes, theprotection mode varies. When one MP reports non-HT mixed mode (the otherreporting protection mode other than non-HT mixed mode) the protectionmethods of the non-HT mixed mode MP will be used for transmissionsbetween these two MPs.

When one MP reports a non-member protection mode of operation and anon-HT mixed mode is not reported by any other MP, the protectionmethods of a non-member protection mode will be used for transmissionsbetween these two MPs. Lastly when one MP reports a 20 MHz protectionmode and neither a non-HT mixed mode nor non-member mode is reported byany MP, then the protection method of 20 MHz protection operations areused for the transmissions between the two MPs.

Accordingly, methodology for determining HT MP protection rules in amesh network can be fashioned. The process begins 305 with determiningwhat type of protection mode is desired and identifying 310 whatprotection modes exist at each mesh point. A query 315 is made to askwhether the mesh point and its neighbor that need to transmit frame within the TXOP possess a common high throughput protection mode. If theresponse is yes, then communications between that mesh point and therelated neighbor is based on the common high throughput protection mode320. In the situation where the HT protection field is to be set to anon-HT mixed protection mode 325 at a mesh point, a determination mustfirst be made that at least one of its neighbor mesh point within themesh network detected on either the primary or secondary channel arenon-HT STA. If this criteria is met, then the HT protection field can beset to a non-HT mixed protection mode 330 for communications between themesh points.

According to another embodiment of the present invention, the HTprotection field can be set to non-member protection mode when it isdetermined 335 that a non-HT STA, detected in either the primary orsecondary channel or in both the primary or secondary channels, is notknown by the MP not to be a member of the mesh network, and all theneighbor mesh points detected in in both the primary or secondarychannels, are HT mesh points. Secondly, a determination is made thatthere is no non-HT mixed mode of HT protection reported by any of thesource mesh point or destination mesh point. If so, the HT protectionfield can be set 350 to a non-member protection mode in the transmissionbetween these two source and destination mesh points.

The HT protection field can also, according to another embodiment of thepresent invention, be set to 20 MHz protection mode 370 when all STAsdetected in the primary and secondary channels by the source anddestination mesh points are HT STAs, and the source or destination MPare HT MPs using 20 MHz protection 360. In addition, the mesh networkcan be determined to be a 20/40 MHz mesh network when at least one 20MHz HT MP is one-hop away from the source MP or the destination MP.

When the HT protection field is not set to a non-protection mode, anon-member protection mode or a 20 MHz protection mode, the HTprotection field is set 390 to a non-protection mode ending 395 theprocess.

Thus, in summary, when two peer HT MPs report the same protection modein their respective HT protection fields, the protection mechanisms ofthe related mode are used to protect the transmissions between the peerHT MPs. When a HT MP and its peer HT MP report different protectionmodes in their respective HT protection fields, one of the followingrules are applied to the transmission between these two mesh points.When a HT MP or its peer HT MP reports a non-HT mixed mode, then theprotection mechanisms of a non-HT mixed mode are used to protect thetransmission between the peer HT MPs. The transmission between peer HTMPs are protected by the mechanisms of the non-member mode when a HT MPor its peer HT MP reports a non-member protection mode and a non-HTmixed mode is not reported by any of the two peer HT MPs. Finally, whena HT MP or its peer HT MP reports a 20 MHz protection mode and neither anon-HT mixed nor a non-member protection mode are reported by any of theHT MPs, then the protection mechanisms of a 20 MHz protection mode isused to protect the transmission between the peer HT MPs.

According to another embodiment of the present invention, STBC can beimplemented to achieve significant error rate improvements over singleantenna systems. FIG. 4 shows a high level flow chart for highthroughput STBC implementation. STBC related operations include dualbeaconing and dual CTS protection. According to one embodiment of thepresent invention, a process for STBC implementation begins 405 with aSTBC MP sending out a non-STBC beacon and, when indicated in the HTinformation element, a STBC beacon. The beacon frame also indicates ifthe dual CTS protection is required for the mesh point transmitting thebeacon frame. If both peer HT MPs set their dual CTS protection field ofthe HT operation element to 1 in the mesh beacon frames 410, then thetransmitter can act as an AP 430 with the dual CTS protection field ofthe HT operation element set to 1 for dual CTS protection procedures.The transmitter may also act as the STA 440 for the dual CTS protectionprocedures.

When a HT MP sets the dual CTS protection field of the HT operationelement to 1 in the mesh beacon frame, and its peer HT MP does not setthe dual CTS protection field of the HT operation element to 1 in themesh beacon frame, the HT MP acts as an AP 450 with a dual CTSprotection field of the HT operation element set to 1 for dual CTSprotection procedures when communicating with its peer MP. By followingthese procedures, HT STBC operational features can be allowed in 802.11smesh networks 495.

20/40 MHz operations can also be included in 802.11s mesh networks.20/40 MHz operations include channel scanning and channel management. AnAP can switch an infrastructure BSS between a 20/40 MHz BSS and a 20 MHzBSS. Moreover a 20/40 MHz independent BSS cannot be changed to a 20 MHzBSS nor can a 20 MHz independent BSS be changed to a 20/40 MHz BSS.

802.11s mesh networks, according to one embodiment of the presentinvention, can support switching between a 20/40 MHz mode and a 20 MHzmode when a robust distributed channel switch mechanism is defined.

When a mesh network switches between 20/40 MHz and 20 MHz, peer MPsrenegotiate mesh coordinated channel access duration parameters. Therenegotiation procedure is started by the mesh point with its workingchannel bandwidth change since, after such channel change, the mediumtime (MCCAOP duration, MCCAOP periodicity) required by the trafficstream also changes. The renegotiation procedure is defined by MCCAprotocol. After such a switch, each MP can accomplish path maintenanceto find an optimized path. If the working channel bandwidth changes, theair-time metric also changes. So the optimized path may also change. Theoptimized path finding procedure is defined by the HWMP protocol.

As will be understood by those familiar with the art, the invention maybe embodied in other specific forms without departing from the spirit oressential characteristics thereof. Likewise, the particular naming anddivision of the modules, managers, functions, systems, engines, layers,features, attributes, methodologies, and other aspects are not mandatoryor significant, and the mechanisms that implement the invention or itsfeatures may have different names, divisions, and/or formats.Furthermore, as will be apparent to one of ordinary skill in therelevant art, the modules, managers, functions, systems, engines,layers, features, attributes, methodologies, and other aspects of theinvention can be implemented as software, hardware, firmware, or anycombination of the three. Of course, wherever a component of the presentinvention is implemented as software, the component can be implementedas a script, as a standalone program, as part of a larger program, as aplurality of separate scripts and/or programs, as a statically ordynamically linked library, as a kernel loadable module, as a devicedriver, and/or in every and any other way known now or in the future tothose of skill in the art of computer programming. Additionally, thepresent invention is in no way limited to implementation in any specificprogramming language, or for any specific operating system orenvironment. Accordingly, the disclosure of the present invention isintended to be illustrative, but not limiting, of the scope of theinvention, which is set forth in the following claims.

While there have been described above the principles of the presentinvention in conjunction with wireless mesh networks, it is to beclearly understood that the foregoing description is made only by way ofexample and not as a limitation to the scope of the invention.Particularly, it is recognized that the teachings of the foregoingdisclosure will suggest other modifications to those persons skilled inthe relevant art. Such modifications may involve other features that arealready known per se and which may be used instead of or in addition tofeatures already described herein. Although claims have been formulatedin this application to particular combinations of features, it should beunderstood that the scope of the disclosure herein also includes anynovel feature or any novel combination of features disclosed eitherexplicitly or implicitly or any generalization or modification thereofwhich would be apparent to persons skilled in the relevant art, whetheror not such relates to the same invention as presently claimed in anyclaim and whether or not it mitigates any or all of the same technicalproblems as confronted by the present invention. The Applicant herebyreserves the right to formulate new claims to such features and/orcombinations of such features during the prosecution of the presentapplication or of any further application derived therefrom.

We claim:
 1. A method for Space Time Block Coding (STBC) in a meshnetwork having a mesh STBC mesh point and at least one neighboring STBCmesh point, the method comprising: determining whether the STBC meshpoint and the at least one neighboring STBC mesh point are highthroughput STBC mesh points; setting a dual clear-to-send (CTS)protection field of a high throughput operation element of the highthroughput STBC mesh points to 1; and responsive to the STBC mesh pointsetting the dual CTS protection field of the high throughput operationelement to 1 and the at least one neighboring mesh point failing to setthe dual CTS protection field of the high throughput operation elementto 1, the STBC mesh point transmitting as an access point with the dualCTS protection field of the high throughput operation element set to 1for communications with the at least one neighboring mesh point.
 2. Themethod for Space Time Block Coding of claim 1, responsive to the STBCmesh point being associated with a high throughput informationalelement, initiating a STBC beacon.
 3. The method for Space Time BlockCoding of claim 1, responsive to the STBC mesh point not beingassociated with the high throughput informational element initiating anon-STBC beacon.
 4. The method for Space Time Block Coding of claim 1wherein the high throughput STBC mesh point is operable to act as anon-access point station during transmission with the dualCTS-protection field.
 5. A high throughput wireless mesh networkcomprising: a plurality of mesh points wherein each mesh point supportsa 20/40 MHz mode of operation; and a protocol operative to switch themesh network from the 20/40 MHz mode of operation to a 20 MHz mode ofoperation.
 6. The high throughput wireless mesh network of claim 5wherein responsive to switching between the 20/40 MHz mode of operationand the 20 MHz mode of operation, peer mesh points renegotiate meshcoordinated channel access duration parameters.
 7. The high throughputwireless mesh network of claim 5 wherein responsive to switching betweenthe 20/40 MHz mode of operation and the 20 MHz mode of operation, eachof the plurality of mesh points conducts path maintenance to identify anoptimized path.